/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.tomcat.util.bcel.classfile;

import org.apache.tomcat.util.bcel.Const;

import java.io.DataInput;
import java.io.EOFException;
import java.io.IOException;

/**
 * Utility functions that do not really belong to any class in particular.
 */
final class Utility {

	private Utility() {
		// Hide default constructor
	}

	/**
	 * Shorten long class name <em>str</em>, i.e., chop off the <em>prefix</em>,
	 * if the
	 * class name starts with this string and the flag <em>chopit</em> is true.
	 * Slashes <em>/</em> are converted to dots <em>.</em>.
	 *
	 * @param str The long class name
	 * @return Compacted class name
	 */
	static String compactClassName(final String str) {
		return str.replace('/', '.'); // Is `/' on all systems, even DOS
	}

	static String getClassName(final ConstantPool constant_pool, final int index) {
		Constant c = constant_pool.getConstant(index, Const.CONSTANT_Class);
		int i = ((ConstantClass) c).getNameIndex();

		// Finally get the string from the constant pool
		c = constant_pool.getConstant(i, Const.CONSTANT_Utf8);
		String name = ((ConstantUtf8) c).getBytes();

		return compactClassName(name);
	}

	static void skipFully(final DataInput file, final int length) throws IOException {
		int total = file.skipBytes(length);
		if (total != length) {
			throw new EOFException();
		}
	}

	static void swallowFieldOrMethod(final DataInput file)
			throws IOException {
		// file.readUnsignedShort(); // Unused access flags
		// file.readUnsignedShort(); // name index
		// file.readUnsignedShort(); // signature index
		skipFully(file, 6);

		int attributes_count = file.readUnsignedShort();
		for (int i = 0; i < attributes_count; i++) {
			swallowAttribute(file);
		}
	}

	static void swallowAttribute(final DataInput file)
			throws IOException {
		//file.readUnsignedShort();   // Unused name index
		skipFully(file, 2);
		// Length of data in bytes
		int length = file.readInt();
		skipFully(file, length);
	}
}
